Rhinovirus C species (RV-C) was discovered in 2006 and is of special interest because RV-C isolates can cause more severe illnesses in children compared to other rhinoviruses and are closely associated with asthma exacerbations. Applicants developed the first culture systems for RV-C (sinus mucosal organ culture and air-liquid interface (ALI) culture of differentiated airway epithelial cells), the first virus production methods (reverse genetics from viral RNA synthesized in vitro) and discovered that human cadherin-related family member 3 (CDHR3) protein mediates virus binding and replication.
Human rhinoviruses (RVs) are classified into three species (A, B and C) of the Picornaviridae family. They are subdivided further into more than 160 types that are responsible for the majority of upper respiratory tract infections (common colds), and also many lower respiratory tract illnesses (Hayden, 2004; Gem, 2010). The first isolates in the RV-C species were described in 2006 (Lamson et al., 2006; Arden et al., 2006). Consequently, they were classified into 55 types, believed to be synonymous with serotypes, according to sequence diversity thresholds observed in the capsid-coding proteins, VP1 and VP4 (Simmonds et al., 2010; McIntyre et al., 2013). The RV-A and RV-C tend to cause more severe illnesses in young children compared to RV-B. However, RV-C infections are those more closely linked with childhood asthma exacerbations (Bizzintino et al., 2011; Calvo et al., 2010; Cox et al., 2013; Drysdale et al., 2014; Fawkner-Corbett et al., 2015; Lee et al., 2012).
Prototype RV-A and RV-B laboratory strains, representing major and minor receptor groups, are commonly used in vitro to study virus biology and host cell response. These include RV-A1 (subtypes a and b), RV-A2, RV-A16 and RV-B14 (Stanway et al., 1984; Skern et al., 1985; Hughes et al., 1988; Kim et al., 1989; Lee et al., 1995). These particular strains have been passaged multiple times in continuous cell lines (such as HeLa) after their initial clinical isolations, and all of them are now available as fully-sequenced cDNA reagents. As a result, the adapted forms of these recombinant viruses replicate well and induce strong cytopathic effect (CPE) in cell culture (Conant & Hamparian, 1968). In contrast, typical unpassaged clinical RV isolates generally replicate less efficiently and without visible CPE in the same cell lines, even though their replication in natural host cells (differentiated airway epithelial cells) remains quite robust (Nakagome et al., 2014).
It has been described that human cadherin-related family member 3 (CDHR3) protein can mediate RV-C binding and replication when it is expressed in cultured cells. A transduced HeLa cell line derivative (HeLa-E8) which stably expresses the CDHR3-Y529 variant supports propagation of RV-C isolates in these cultures after infection (Bochkov et al., 2015). The HeLa-E8 cell line propagation method is the subject of pending U.S. patent application Ser. No. 14/836,327, incorporated herein in its entirety. C15, a recombinant derivative of a clinical RV-C isolate (Bochkov et al., 2011) replicates to detectable titers in HeLa-E8, yet the progeny yields of this virus after infection never reach the levels achieved in parallel infections by RV-A or RV-B adapted laboratory strains. Moreover, C15 infections of HeLa-E8 cells do not induce visible CPE, a useful phenotypic marker of effective, productive viral synthesis.